1. Field of the Invention
The present invention relates to an apparatus for laser treatment by irradiating therapeutic laser beam to an eye of a patient.
2. Description of the Related Art
An apparatus for laser therapy for coagulation by irradiating therapeutic laser beam to an eye of a patient is well-known so far. A variety of wavelengths of therapeutic beam from the laser therapy apparatus are used, ranging from visible light to infrared. The selection of the wavelength of therapeutic laser beam is made by taking account for the absorption characteristics of the area to be cured.
When, for example, an attempt is made to treat a retinal separation at an ocular fundus by coagulation through such layers as intraretinal, retinal pigment epithelium (called as "pigment epithelium" in the specification below), and choroid, one wavelength results in selective coagulation of one layer. This means that a shorter wavelength may strongly coagulate the intraretinal layer, whereas a longer wavelength may coagulate primarily the choroid layer. In order to obtain a coagulation from an intra-layer to a fundus layer, laser beams of different wavelengths must be irradiated. As the different wavelengths are irradiated by separate operation, laser irradiation to the identical site to be treated may be so difficult that the efficiency will be poor. Further, if laser beam of a longer wavelength is irradiated after a shorter wavelength, a degenerated and coagulated layer prevents laser beam from penetrating into deeper layers.